1. Field of the Invention
This invention relates to a telecommunications method and a suitable system for establishing a connection with a mobile device. In particular, it relates to a telecommunications method, and a system suitable therefor, for establishing a connection with a mobile device of a participant who is located in a visited PLMN (Public Land Mobile Network), for example in a foreign VPLMN.
2. Discussion of the Background
To calculate the costs of a telephone connection, whether for a telephone call or for data transmission, so-called call data records (CDRs) are typically sent to a billing system. The calculated costs, which are dependent upon different parameters such as point in time, duration, place or distance, are charged to the respective participant by the billing system. In a method with prepayment, the costs are deducted from a prepaid amount, whereas in a method with subsequent payment (postpaid), the costs are collected from the respective participant through invoice. In particular in a GSM mobile radio network, the call data records typically arrive for billing at the billing system only after a time lag. In the case of call data records from abroad, this time lag can very well be even longer. For prepaid systems, this time lag can be problematic because it is thereby possible for a participant to phone free of charge during this time lag when actually his prepaid credit has already run out. Solutions in which the credit of a participant is tracked directly and in real time, for example on his SIM card inserted into the mobile device, are considered too insecure by many operators because they believe that such cards are susceptible to fraudulent manipulations. In general, the problem is circumvented by the network operators in that outgoing calls (originating calls) of a mobile participant who is stationed in a VPLMN, for example a foreign PLMN, are blocked, for example in the HLR of the HPLMN of the mobile participant. For the affected mobile participant, this solution is understandably unsatisfactory.
Described in the patent application WO 97/29609 is a method for establishing a voice link between a subscriber to a mobile radio network and a partner on the voice channel of a mobile terminal, in which method data necessary for setting up the call are transmitted over an additional data channel accessible to the terminal, in particular the SMS (Short Message Services) channel. According to the method described in WO 97/29609, the call is set up via a monitoring computer connected to the terminal, which computer automatically dials a call number obtained via the data channel or transmits a data message to a remote station for initiation of a voice link by this remote station.
Described in the patent application WO 97/50237 is a method and a system for validating a forward-to-number within a mobile telecommunications system. According to the method described in WO 97/50237, a forwarding request is transmitted to a mobile switching center (MSC) by means of a USSD (Unstructured Supplementary Services Data) message, which mobile switching center, through a call back to the mobile station and through a call to the telephone terminal associated with the forward-to-number, establishes a voice link between the mobile station and the telephone terminal, so that the mobile subscriber can verbally verify the forward-to-number.